From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 5 May 2009 11:10:29 +0000 (+0200)
Subject: Fix missing pawn color check in move_is_legal()
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=46bb6c6dc300bc5a8b819d690734ddcb1f1e4e14;ds=sidebyside

Fix missing pawn color check in move_is_legal()

In case we have a correct white pawn move but pawn
is black (or the contrary) we fail to detect the
move as illegal.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/movegen.cpp b/src/movegen.cpp
index b3a25806..9a6b902b 100644
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -496,6 +496,11 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
   // Proceed according to the type of the moving piece.
   if (type_of_piece(pc) == PAWN)
   {
+      // Move direction must be compatible with pawn color
+      int direction = to - from;
+      if ((us == WHITE) != (direction > 0))
+          return false;
+
       // If the destination square is on the 8/1th rank, the move must
       // be a promotion.
       if (   (  (square_rank(to) == RANK_8 && us == WHITE)
@@ -505,7 +510,7 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
 
       // Proceed according to the square delta between the source and
       // destionation squares.
-      switch (to - from)
+      switch (direction)
       {
       case DELTA_NW:
       case DELTA_NE: